There are many and diverse systems for the manipulation and operation of robotic end effectors which are subject to control by a human operator relying on visual observation or television viewing of the target. Where such means of control are impractical, systems have been devised which employ proximity sensors for providing sensory input signals regarding the location and relative orientation of the target with respect to the end effector. Such sensors are frequently of the non-contact type which send energy pulses or beams, typically optical or ultrasonic, to a target to be grasped. The sensors are adapted to receive reflected energy from the target and generate electrical signals in response thereto and from which ranging and direction information can be input to an automatic control system or employed by a human operator for adjusting the orientation and range positioning of the end effector with respect to the target.
Another known method and system for positioning and controlling a robotic hand in the act of grasping a target employs the beam break technique in which optical beams are established between the fingers of the end effector. Interruption of the optical beams as the target enters the grasp region is used to signal the end effector to close and it can also be used to command the end effector to open. A disadvantage of the beam break technique is that it does not provide range information which is necessary for the proper positioning of the end effector with respect to the target. Since the proximity sensor's transmitter and receiver are located on different fingers of the robotic hand, proper alignment between the transmitter and receiver becomes critical since improper alignment limits the end effector finger motion and also limits the possible grasp configurations of the robotic hand. With such limitations, a successful reliable grasp of the target may be extremely difficult, if not impossible. The beam break technique can also produce a premature closure of the end effector if the target enters the grasp region at a low speed.
U.S. Pat. No. 3,423,765 discloses a prosthetic device with contact sensor means in the finger tips of a robotic hand for signaling slippage from the grasp of the device and responsive electronic means for controlling the grasping action.
U.S. Pat. No. 4,674,057 uses ultrasonic ranging transducers on the end of a robotic arm in a safety system for sensing obstruction to the motion of the robotic arm and for halting operations until the obstruction is removed.
U.S. Pat. No. 4,718,023 discloses apparatus for positioning a robot hand at a predetermined distance and orientation with respect to a reference surface and which includes transducers for sending acoustic pulses and receiving reflected signals.
U.S. Pat. No. 4,660,829 discloses a system for body joint position monitoring wherein light emitting diodes on one body member transmit light beams for detection by an array of photocells on the other body joint member.
U.S. Pat. No. 4,602,163 utilizes an external reference coordinate system wherein laser beams in orthogonal planes are directed by mirrors to detectors on a robot hand which transmit signals to a robot control system.
U.S. Pat. No. 4,260,187 discloses a system wherein four distance measuring sensors located on an end effector at the corners of an imaginary square detect target distances. The detector signals are used in a control system for adjusting orientation of the end effector.
A publication by Charles Wampler, "Multiprocessor Control of a Telemanipulator with Optical Proximity Sensors", The International Journal of Robotics Research, Vol. 3, No. 1, Spring 1984, discloses a telemanipulator equipped with optical proximity sensors and a multiprocessor in a closed-loop control system.
U.S. Pat. No. 3,888,362 discloses apparatus for grasping an article with a system which controls positioning and orienting of the end effector prior to a final grasping action. Light emitting diodes on orthogonal axes of the grasping element are sequentially energized and the light therefrom reflected by the target to a photosensor. Signals from four quadrants of the photosensor are used to align orthogonal axes of the sensor with the target axes.
U.S. Pat. No. 2,567,066 discloses a robotic hand with solenoids located on each finger in inner and outer rows, of which rows may be sequentially activated by a human operator to work the finger joints to release an object.
In many of the foregoing disclosures, it is to be noted that a target of specific size and configuration is oftentimes required for an end effector to effect a reliable grasp of the targets. Also there is no capability for providing an autonomous, non-contact, prepositioning of a dexterous robotic end effector with respect to targets of different shapes and contours so as to minimize target escape potential during grasping.